This invention relates to containers and has particular reference to containers for use on pallets. The conventional ways of shipping material, which is fluid by nature, either liquid or powder, normally comprise the use of small drums of 25 liters or 150 liters size or requires the use of bulk tankers capable of handling large volumes of liquid or other fluids. The bulk tankers are normally returned to base for refilling or reloading whereas the small containers are often regarded as disposable. Because of the cost of handling there is a requirement to increase the size of the small bulk containers without doing away with the advantages of the use of disposable containers. The present invention has particular application to containers capable of carrying loads of the order of one ton and being used on a standard sized pallet.
In British Patent Specification No. 1 400 414 there is described the use of a container of approximately the same size as that used for the present invention which comprises a double-skinned container with a wooden reinforcing strut located vertically in the centre of each face of the container between the skins. The skins are both structural members and the fluids are retained inside by means of a separate bag which is not shown specifically in the drawings of the patent specification. It has been found that there are differences in using containers of the type described in the above mentioned British patent for liquids as opposed to powders. By their very nature liquids are more mobile than dry powders and the container may be regarded as being more "active" during transport. The present applicants have found that although such a container is suitable for transporting dry powders it is necessary, when transporting liquids, to provide a restraining collar to support the container in use. Otherwise it has been found that the container can fail during transport. Experiments have illustrated that a restraining band of the order of 21/2 cm.sup.2 of steel is sufficient to have strength to carry out the necessary restraining effect. It has also been found desirable to provide a 21/2 cm.sup.2 rim around the pallet on which the container sits. Unfortunately the use of such restraining collars has two disadvantages. The first is the economic disadvantage in providing the collar, both in material costs, fabrication costs and handling costs. The second, perhaps more serious, is the loss of volume associated with the loss of the exterior 21/2 cm thick zone which is occupied by the collars and which could otherwise be useful for the transport of liquid. The loss of volume associated with the use of 21/2 cm.sup.2 collars on a pallet 1 m.sup.2 is 7 or 8%.
In British Patent Specification No. 1 467 884 there is described a modification of the invention described in British Patent Specification No. 1 400 414, in which the upright struts are secured to the outer skin by means of a turn buckle. Again, the invention described in British Patent Specification No. 1 467 884 requires the use of two structural skins which are separated by the upright struts.
To the best of the Applicant's belief there are no known containers for liquids capable of being used on a standard ISO pallet (1 m.sup.2) which are formed basically of a fibre or cardboard exterior having a simple plastics liner. There are many proposals for using cardboard boxes to contain materials, and proposals have been made, see UK Patent Specification No. 2 024/1913, to use wires to strengthen cardboard boxes such as hat boxes or drawers. However, such systems would not be useful for semi-bulk containers of a size intended to be used on an industrial pallet.
In UK Patent Specification No. 883 762 there is described a reinforced fibreboard container being formed of inner and outer fibreboard layers, but there are no provisions to permit the box to withstand the pressures found in semi-bulk containers for liquids.
UK Patent Specification No. 1 279 232 is concerned with composite boxes having a capacity in the region 100-200 gallons, but proposes the use of expensively machined corner portions to withstand the pressures attendant upon the use of fibreboard for the external shell of the container.
In UK Patent Specification No. 1 295 831 a stillage bin is provided in which internal pressures are resisted by an external framework provided around the container.
UK Patent Specification No. 1 297 915 proposes a container in which wooden posts are used in the corners to support the corners of the container.
UK Patent Specification No. 1 378 507 proposes a container in which rigid reinforcing elements are secured to the faces of the panels in a horizontal plane.